The NF-104 aerospace trainer is a modified F-104A airplane, incorporating a
liquid fuel rocket engine in addition to the conventional turbojet engine. The
modification was done to allow flight in regimes and under conditions not
obtainable with available operational airplanes. The aircraft is used to provide
spaceflight training at a fraction of the cost of fully rocket-powered research
aircraft.

The NF-104's extra power comes from a 6,000-pound thrust rocket engine built
into the tail of the aircraft which allows the plane to reach altitudes of over
120,000 feet where the atmospheric pressure is only one-one hundredth that of
the earth's surface. Control at these altitudes is accomplished through the use
of hydrogen peroxide controls which are used to maneuver the craft just as is
the case with the X-15 and
manned space capsules orbiting the earth.

Other modifications to the aircraft include the extension of the wing tips 24
inches to house the reaction control jets that act as ailerons to control roll
in the thinner air and the substitution of a larger vertical tail and the
forward extension of the engine air inlet cone for better pressure recovery and
thrust. The nose cone also contains reaction control jets for pitch and yaw
control at high altitudes.

The aircraft enables pilots to experience the effects of zero gravity flight
in addition to the previously mentioned operational advantages. This zero
gravity or zero "Gs" as it is commonly called, is accomplished through what is
called a zoom maneuver whereby the aircraft flies a ballistic arc, and in going
"over the top" the pilot experiences over a minute of weightlessness or no
gravity.

The NF-104 Space Pilot Trainer

Back in the 20th century when service stations provided service, women dressed like
women , and 4-wheel-drive vehicles were used as 4-wheel-drive vehicles, the
USAF added a rocket powered airplane to its inventory. Maybe the NF-104 did not
fly as fast and as high as the Mercury, Vostok, or the X-15, however, the NF-104
was far less expensive to operate. Capable of takeoff/landing from conventional
runways under its own power, this aerospace plane was a low cost and quick means
to skim the boundaries of space. And, it was fully reusable as a trainer for
X-15 spaceplane and X-20 DynaSoar pilots (the X-20 was a small delta-wing
orbital “space shuttle” that was cancelled in 1963).

The NF-104 is a modified F-104, with a 6,000-pound thrust liquid fuel rocket
engine in addition to the conventional jet engine.

NF-104 zooming
skyward, awesome photo, eh?
Check out that flame!

This plane can reach altitudes over 120,000 feet where the atmospheric
pressure is virtually a vacuum, and for all practical purposes, this is space.
Control at these altitudes is accomplished with hydrogen peroxide reaction
control jets for pitch and yaw, used to maneuver the craft just like the X-15
and manned space capsules orbiting the earth. When this aircraft flies a
ballistic arc, and in going “over the top” the pilot experiences over a minute
of weightlessness or no gravity. On November 1963, Major R.W. Smith set an
altitude record of 118,600 feet. Smith also took it to 120,800 feet the
following month but Guiness does not accept this as it did not exceed by 3% as
required by FAI for world records.

Because it flys to the edge of space, pilots of the NF-104 have to wear spacesuits, just
like “real” astronauts. Above 60,000 feet, the human body cannot tell the
difference between this altitude or 100 miles; you’ll be just as dead without a
spacesuit.

So where are the NF-104s these days? Serial #60762 was lost when tested by
Yeager (see below), Serial #60756 was scrapped after its rocket exploded,
removing half of its rudder, and Serial #60760 is mounted on a pylon by the USAF
Test Pilot School at Edwards AFB.

A fourth NF-104 was to be built but never got the rocket on the tail because
the project was terminated. Years later, this F-104 became a old boneyard heap
of junk from out of Maine, and was purchased by a team working to set a new
landspeed record. They are rebuilding and modifying this airframe to travel 800
mph on the ground.

The NF104 by the USAF Test Pilot School lacks RCS thrusters. The reason for
lack of the thrusters was because they are not on the aircraft anymore. In the
late seventies Darryl Greenamyer purchased and modified an F-104 that he planned
to use to set several speed and altitude records. This was the famous “Red
Baron” F-104. In 1978 he somehow convinced the powers that be at Edwards to
“loan” him the nose and wingtips off of the NF-104 on display there with the
promise that they would be returned unharmed. He was allowed to remove them and
had installed them on his airplane when, in late 1978, he was forced to eject
from his aircraft and the plane was destroyed.

Click on Picture to enlarge

NASA's Lockheed F-104 Starfighters served long & well. For
the X-15 & Lifting Bodies, pilots trained in low lift/drag-ratio landings in
'104s-cut the power, drop the flaps/gear & pop the speed brakes, and an F-104
flies like a piano-just like an X-15 or Lifting Body! In the chase role, the '104's astounding
rate of climb allowed it to keep pace with the X-15, and since the pilots flew
those training approaches in '104s, they could keep up at landing as well. Even
after the USAF retired the "Zipper," NASA kept a few, like this 2-seat F-104B,
at Dryden Flight Research Center (Edwards); NASA didn't retire their F-104s
until 1994, 40 years after the type's first flight. NASA Photo.

Click on Picture to enlarge

Although not a NASA
aircraft, the NF-104A Aerospace Trainer was flown by many astronauts that
graduated from the USAF Aerospace Research Pilots School (ARPS), run by Chuck
Yeager at Edwards in the '60s. The NF-104 was modified to give students the feel
of rocket flight, reaction controls, & extreme altitudes. This version of the
Zipper featured a 6,000-lb thrust rocket engine in the tail, in addition to the
powerful J-79 jet engine that gave the '104 its already amazing power &
performance. The added boost could propel the jet through a zoom climb ending
well north of 100,000 ft, far past the point where the J-79 had to be shut down
to prevent overtemping. The NF was outfitted with a special nose and wingtips
that housed reaction control thrusters, for maneuvering at high altitudes where
the control surfaces no longer worked. 3 NFs were made; Yeager was badly injured
bailing out of one, when he discovered the dead band in the control system: too
high for aerodynamic surfaces, too low for thrusters. He had no contol in that
altitude range, and entered a spin. He fought for control, but had to eject, and
was badly burned when the rocket end of the seat hit him on the way down. This
incident was portrayed with a standard '104 at the end of The Right Stuff.
Only 1 NF survives, a gate guard at the USAF Test Pilot School at Edwards.
The type was retired when ARPS closed in the early '70s. USAF Photo.

The NF sat for several years with a standard fiberglass nose, but recently a
metal nose with the long YAPS boom was installed on it and although it still has
no RCS thrusters it looks much more appealing now.

The X-37 will use the same rocket engine as the NF-104. Here is a quote
straight from the X-37 press release: “The X-37’s on-orbit propulsion is
provided by the AR-2/3, a high reliability engine with a legacy stretching back
to the 1950’s. It can produce 7,000 pounds of thrust. Hydrogen peroxide and
JP-10, a grade of kerosene commonly used as jet fuel, will propel the X-37
engine.”

Lockheed NF-104A Starfighter

Joe Baugher

In 1963, three ex-USAF F-104As (56-756, -760, and -762) were taken out of
storage at Davis Monthan AFB and modified as NF-104A aerospace training
aircraft. All of the military equipment was removed and the original F-104A
vertical fin was replaced by the larger fin that was used on the F-104G. The
wingspan was increased by four feet (to 25.94 feet) and a set of hydrogen
peroxide control thrusters were mounted at the nose, tail, and wingtips. A 6000
pound thrust Rocketdyne LR121/AR-2-NA-1 auxiliary rocket engine was mounted on
the tail above the jet exhaust pipe. This rocket engine could be throttled from
3000 to 6000 pounds of thrust, and the burn time was about 105 seconds.

The first NF-104A was delivered on October 1, 1963, with the other two
following a month later. They were operated by the Aerospace Research Pilot
School at Edwards AFB, which was commanded at that time by Colonel Charles E.
"Chuck" Yeager.

On December 6, 1963, the first NF-104A set an unofficial world altitude
record of 118,860 feet for aircraft taking off under their own power. The
official record at that time was 113,829 feet, set by the Mikoyan/Gurevich
Ye-66A, an experimental version of the MiG-21 Fishbed. Later, the same NF-104A
flown by Major R. W. Smith reached an altitude of 120,800 feet.

On December 10, 1963, the second NF-104A (56-762), with Chuck Yeager at
the controls, went out of control at an altitude of 104,000 feet and fell in a
flat spin to 11,000 feet. Yeager managed to eject successfully at that altitude,
although he was badly burned on his face by the rocket motor of his ejector
seat. The aircraft was destroyed in the ensuing crash. An investigation later
showed that the cause of the crash was a spin that resulted from excessive angle
of attack and lack of aircraft response. The excessive angle of attack was not
caused by pilot input but by a gyroscopic condition set up by the J79 engine
spooling after shut down for the rocket-powered zoom climb phase. So it wasn't
Chuck's fault.

In June of 1971, the third NF-104A, with Capt. Howard C. Thompson at the
controls, suffered an inflight explosion of its rocket motor. Although Thompson
was able to land safely, the aircraft's rocket motor and half its rudder were
blown away. Since the program was about to end in any case, this aircraft was
retired.

The number one NF-104A is currently on display on top of aa pylon in front
of the USAF Test Pilot School.

The Lockheed NF-104A was an American mixed power, high-performance,
supersonic aerospace trainer that served as a low cost astronaut training
vehicle for the X-15
and projected X-20
Dyna-Soar programs.

Development

With the advent of manned spaceflight in the early 1960s, the United
States Air Force Experimental Flight Test Pilot's School at Edwards Air Force
Base was renamed the Aerospace Research Pilots School (ARPS), with the
emphasis on training moving away from the traditional test pilot course to a
more spaceflight oriented curriculum.[1]

Initial Use Of The F-104

A number of standard production F-104 Starfighter
aircraft were obtained and used by the ARPS to simulate the low lift/high drag
glide approach path profiles of the X-15 and the
projected X-20 Dyna-Soar
program. These maneuvers were commenced at 12,000 ft (3,700 m) where the F-104
engine was throttled back to 80% power; and with the flaps, speedbrakes and
landing gear extended, the aircraft was established in a 30˚ dive with a
pull-out for the landing flare starting at 1,500 ft (460 m) above the ground.
These glide approaches gave little room for error. A modified Gulfstream G-II
has been used by NASA for similar training for the Space Shuttle program.

The Reaction Control System

Click on Picture to enlarge

JF-104 during RCS testing.

It was realized that normal aircraft control surfaces had little or no
effect in the thin atmosphere of the stratosphere and that any aircraft
operating at extremely high altitudes would need to be equipped with a
reaction control system (RCS). A modified version of the
Bell X-1 was used for initial RCS
tests, but was grounded after technical problems and was replaced with a
NASA-modified Lockheed F-104A (55-2961) in 1959 which carried RCS systems on
its wing tips and in the fuselage nose. This aircraft (designated JF-104)
achieved a maximum altitude of 83,000 ft (25,000 m) during the test program.
Pilots who flew this aircraft included Neil Armstrong who gained valuable
experience in using the RCS system. Pilots complained that the instrument
displays were difficult to read and were not accurate enough for the critical
zoom climb profiles required to reach high altitudes.[2]

The Lockheed Contract

Lockheed was awarded a contract by the USAF to modify three F-104A
aircraft for the dedicated role of aerospace trainer (AST) in 1962. The
airframes were taken out of storage at AMARC and transported to the company
factory for modification.

Aircraft Design And Flight Profile

The F-104A design was already established as a lightweight, high
performance aircraft; but for the AST project, emphasis was placed on removing
unnecessary equipment, fitting a rocket engine to supplement the existing jet
engine, fitting an onboard RCS system and improving the instrumentation
required. The following details give the main differences between the
production version and the AST:

Wing Modifications

The wingspan of the NF-104A was increased by adding tip extensions to
the existing planform. This modification was needed to house the RCS roll
control thrusters and would also decrease the type's wing loading.

Tail Surface Modifications

The vertical fin and rudder were replaced by the larger area versions
from the two-seat F-104 and were structurally modified to allow installation
of the rocket engine.

Fuselage Modifications

The fibre glass nose radome was replaced with an aluminum skin and
housed the pitch and yaw RCS thrusters. The air intakes originally designed by
Ben Rich were of the same fixed geometry as the F-104A but included extensions
to the inlet shock cones for optimum jet engine operation at higher Mach
numbers. Internal fuselage differences included provision for rocket fuel
oxidizer tanks, deletion of the M61 Vulcan
cannon, Radar equipment and unnecessary avionics. A nitrogen tank was
installed for cabin pressurization purposes, this was required as there would
be no bleed air available from the engine after its normal and expected
flameout in the climb phase.

The Rocket Engine

In addition to the standard J79 jet engine a
Rocketdyne AR2-3 rocket engine was fitted at the base of the vertical fin.
This engine burned a mixture of JP-4 jet fuel and hydrogen peroxide oxidizer.
The NF-104 carried enough oxidizer for 100 seconds of rocket engine operation.
The thrust level could be adjusted by the pilot using an additional throttle
lever on the left side of the cockpit.

The Reaction Control System

The Reaction Control System or RCS consisted of eight pitch/yaw motors
(four for each axis) and four roll motors. They used the same hydrogen
peroxide fuel as the main rocket engine and were controlled by the pilot using
a handle mounted in the instrument panel. The pitch/yaw motors were rated at
113 lbf (500 N) thrust each and the roll motors were rated at 43 lbf (190 N)
thrust.

The Typical Flight Profile

The NF-104A was able to reach great altitudes through a combination of
zoom climbing (trading speed for altitude) and use of the rocket engine. A
typical mission involved a level acceleration at 35,000 ft (11,000 m) to Mach
1.9 where the rocket engine would be ignited, and on reaching Mach 2.1 the
aircraft would be pitched up to a climb angle of 50 to 70 degrees by carefully
applying a load equal to 3.5 g. The J79 afterburner would blow out at
approximately 70,000 ft (21,000 m) followed shortly after by flameout of the
main jet engine itself through lack of oxygen. After continuing over the top
of its ballistic arc the NF-104 would descend back into denser air where the
main engine could be restarted using the windmill restart technique for
recovery to a landing.[3]

Operational History

The First NF-104A

The first NF-104A (USAF 56-0756) was accepted by the USAF on 1
October 1963. It quickly established a new unofficial altitude record of
118,860 ft (36,230 m) and surpassed this on 6 December 1963 by achieving an
altitude of 120,800 ft (36,800 m). It suffered an in-flight rocket motor
explosion in June 1971. Although the pilot was able to land safely, the
damaged aircraft was retired and marked the end of the NF-104 project. This
aircraft was reported as scrapped.

The Second NF-104A

The second NF-104A (USAF 56-0760) was accepted by the USAF on 26
October 1963. After retirement, this aircraft was mounted on a pole outside
the U.S. Air Force Test Pilot School at Edwards Air Force Base and can still
be seen there today. The extended wing tips, RCS metal nose cone and other
parts from 56-0760 were loaned to Daryl Greenamyer for his civilian
aviation record attempts using a highly modified F-104. When he was forced to
eject during a record flight, his aircraft was destroyed and the parts were
never returned.[4]

The Third NF-104A

The third NF-104A (USAF 56-0762) was delivered to the USAF on 1
November 1963, and was destroyed in a crash while being piloted by
Chuck Yeager on 10 December 1963.
This accident was featured in The Right Stuff motion picture; although the
aircraft used for filming was a standard F-104G flying without tip tanks.[5]